During manufacture of containers of food, beverage, tea, etc., it is usually required to apply antiseptic gels to the closures of the containers, such as can lids, in order to enhance the antirust property of the closures. After applying antiseptic gels, the closures need to be dried, usually in a drying chamber. Such closures are usually made of thin pieces of metal, and of light weight. Traditionally, these thin piece closures are conveyed by flat belts to and from drying chamber, on which closures are easily hit and/or stick to each others, significantly lowering the quality of the impacted closures.
Chinese Patent Application Publication No. CN101221013, published on Jul. 16, 2008, discloses a method for drying can lids using a high-frequency induction stove. In this method, can lids are conveyed in the induction stove while in a magnetic suspension state. A photoelectric displacement sensor is used to transfer the displacement information of the can lids to a control system, thereby heating the can lids in a controllable manner. However, the implementation of magnetic suspension complicates the system design. Moreover, due to differences in the shape and/or weight of can lids, different control schemes have to be adopted, thus making the conveying process rather difficult to control.
Traditionally, thin piece metal closures, such as can lids, are dried when they are conveyed through a resistive heating tube or gas heating chamber. Such drying/heating methods suffer from high energy consumption and long drying period. In addition, because the antiseptic gels are usually adhesive, closures may stick together after dried by such traditional methods, lowering the product quality. Chinese Patent Application Publication No. CN1103042C, published on Mar. 12, 2003, discloses a method similar to the traditional ones.